What bacterial infection affects hair follicles and results in pustules and erythema?

Folliculitis is the correct answer as it specifically refers to the infection and inflammation of hair follicles, which can lead to the formation of pustules—small, pus-filled bumps—and erythema, or redness of the skin. This condition is typically caused by bacteria, most commonly Staphylococcus aureus, and often manifests in areas of the body where hair follicles are present, such as the scalp, beard area, and legs.

In contrast, pustulosis generally refers to a skin condition characterized by pustules but is not specifically linked to hair follicles. Contact dermatitis is a skin reaction caused by exposure to allergens or irritants, leading to red, itchy, inflamed skin, but it is not an infection. Cellulitis is a deeper infection involving the dermis and subcutaneous tissue, often presenting with redness, swelling, and pain, but it is not limited to hair follicles and does not primarily manifest with pustules. Therefore, folliculitis is the condition that uniquely focuses on the infection of hair follicles, making it the most accurate choice for this question.